Warning: Don’t store Blu-ray discs in Sleeves & Heat Gun Revival Technique

Towards the end of last year, I posted a warning about not stacking Blu-ray blanks in sleeves, after being devastated at losing a good number of “fresh” blank TDK BD-R DL discs I paid a good amount for.

It seemed that storing them in sleeves, under pressure, may have caused damage to the coating causing them to fail burning and come out of the burner with a spotty pattern.

Comments included not using PVC sleeves, which is sensible advice since the CD days as PVC outgasses and has a tendency to “stick” to the top foil data layer on CDs and “peels” them off causing permanent destruction. Of course, most sleeves since then aren’t made with PVC.

Albert, a senior moderator at MyCE forums warned:

The sleeves were known to make things go bad after the discs had already been written; good to have confirmation that it can affect things before burning them, too.

The folks who have had issues with storage of previously written discs have been able to revive them with a heat gun to undo the pattern left by the sleeves. I’m not sure if the same revival technique could have helped, or if there was more damage done than just that.

cd pirate, a MyCE resident replied:

I’ve also noticed this myself back in the DVD days.

You don’t need to have anything pressed on top either. Sometimes just the pressure of having two discs back to back in a cd/dvd wallet with the whole wallet filled with discs can cause it.

Some wallets are tighter than others too. I’m currently using a sleeve system but the discs are stored upright with no pressure from other discs so we’ll see if that causes any indentation.

BD-R discs “hard coat” probably gets more messed up than cd/dvd too. It’s probably just a lacquer or something cheap. Would have been nice if the plastic itself was scratch proof.

I never had such issues back in the DVD days myself, so I didn’t pay much attention to it. I had already read back over 90% of my BD-R collection to hard disk because of a lack of trust in the discs, so I only had about 30 discs to do. Unfortunately, I had some important things to do immediately, so I left the discs on a shelf and forgot all about them until just recently.

Finishing the Copy Operation

All of the discs that needed to be copied were about 6-year old burns from my LG GGW-H20L. They were stored in PP sleeves (not PVC) and were mostly stored vertically so as not to have pressure pushing against them by stacking. Most of them were TDK Made-in-Japan discs, with only a few CMCs mixed in.

Starting the copy operation, I got read errors on quite a few discs. Looking at the bottom, the dreaded issue which showed with the blank discs reared its head again.

20150413-1336-4555

The pattern is hard to observe, especially with a camera, and can only be seen at the edges of bright direct light. It tends to be a cross-hatch pattern corresponding to the patterning on your sleeve material, which cannot be cleaned off the disc using microfibre cloth, or even with high-purity ethanol.

This seems to affect the discs I had stored in sleeves both vertically and horizontally, generally being worse for discs which had been stored for long periods without removing and rotating.

My hypothesis as to the cause goes as follows:

  • The data layer sits much closer to the bottom in a Blu-ray disc, covered by a 0.1mm polycarbonate and hard-coat cover. This is barely the thickness of two sheets of paper, or a sheet of laminator plastic.
  • The thin cover layer has some pliability, as most thin pieces of plastic do. You can prove this to yourself by carefully flaking off a portion of the bottom layer and trying to pull on it or push into it – it will stretch and dent.
  • The sleeves are made of plastic which may chemically react or degrade over time causing outgassing which condenses on the surface and may react with the hard coat to form more “opaque” spots which affects the readout laser.
  • The uneven surface may exacerbate this as the pliability would result in a pattern being “written” into the thin layer, affecting its refractive index (potentially) and the focus of the laser (more likely), resulting in a “pattern” of errors in readout. If the errors are dense enough, data is lost.

I really wanted the data back, so being the desperate person that I was, I decided to follow some advice given by Albert – after all, I didn’t have much more to lose.

Heat Gun Treatment

For the heat gun treatment, I decided to just experiment and see what happens. I used my Tenma SMD Rework station, which has a temperature controlled gun. I set the temperature to 180 degrees Celsius, ensured no concentrating nozzle was installed and set the flow to 75/100.

Before beginning, it’s worthwhile to clean the surface of the disc to remove all contaminants, and then blow using a photographic blower bulb to remove all the remaining dust.

I placed the disc with the data side facing up on my flat wooden desk, and waved the tip of the heat gun about 5cm above the data surface in a circular motion, making sure to move around the disc continually to avoid concentrating the heat too long at one particular spot.

Remember that we want to get the plastic hot enough to become a little more pliable to hopefully restore its shape and state, but we don’t want to expose the data layer to too much heat because that will destroy the data. The heating may have a secondary benefit in evaporating any outgassed contaminants that might otherwise have adhered to the surface.

Generally, you won’t need to use the gun for more than 20 seconds at a time as the substrate will begin to warp very quickly, causing it to “rise” near the centre hub ring. If the substrate sets “deformed”, this can affect readability, so I tend to stow the gun and then immediately put my fingernails on the centre of the hub and push down towards the desk to ensure the disc “sets” relatively flat.

You will notice a slight improvement in the surface condition, but it will not restore the surface to perfect flatness. That is not the aim of the process – the aim is just to restore enough readability to recover the data.

In order to gauge the improvement – I took the scans of six bad discs before the treatment and immediately after the treatment.

Disc 1

Disc1-SleeveReadErr Disc1-AfterHeating

After heating, the scan doesn’t look particularly appetizing, but it is readable. I was a little cautious, so I decided to go relatively quick with heating. The improvement is apparent, with a more than halving of the error rate.

Disc 2

Disc2-SleeveReadErr Disc2-AfterHeating

This one I gave a little more heat because of the bad state of the before scan. Unfortunately, it seems that the outer edge didn’t respond so well to the treatment, and retained its high rate of error. This may have been because of the original burn, thus giving us a clear reason as to aim for better burns as that increases the margin available for degradation. The first half of the disc after treatment is barely even passable for a fresh burn after 6 years.

Disc 3

Disc3-SleeveReadErr Disc3-AfterHeating

This disc was not as bad as the others in the middle, but the edge seemed to have issues yet again. Despite the horrid scan, it was possible to read back all the data, although not at full speed.

Disc 4

Disc4-SleeveReadErr Disc4-AfterHeating

This one seems like another particularly bad disc, even after heating it with the gun, but it restored it all to under 80 BIS which seems to be the safe threshold for readability in my experience. The reduction in error rate is pretty dramatic however.

Disc 5

Disc5-SleeveReadErr Disc5-AfterHeating

Again, improvements towards the edge seem more limited, suggestive of disc degradation, dirt or other influences such as warpage which may affect readability. I did apply additional heat for this round to try and see whether this could be improved upon over the previous samples where I presumed the outside may not be getting enough heat, but it didn’t seem to make any difference. On the upside, the disc did not bubble, smoulder or get damaged despite the rougher treatment.

Disc 6

Disc6-SleeveReadErr Disc6-AfterHeating

Another outcome, pretty similar to Disc 5. This makes six out of six heat gun successes – all discs did not read correctly and had CRC errors prior to the heat gun treatment, and all of them were read successfully afterwards.

This shows the value of optical disc scanning. Even if you can’t relate the readouts of the test to industrial test equipment, it still provides a relative gauge of how easy or hard a disc is to read using a particular drive assembly. With digital error correction, a “cleanly” viewed signal after error correction could be moments away from failure. This is the same reason why you have signal quality bars on your digital TV receiver, and noise margin stats on your ADSL modem.

While the discs were read and recovered successfully, they did not exhibit the same readability margins expected of good fresh burns or even degraded properly-stored burns. As a result, these “recovered” discs should be considered expired and due to be disposed, and this is just a last ditch effort to recover the data.

However, it also lends support to my observation that the test thresholds we use are too stringent – in all cases, the after scan was readable on the LG GGW-H20L with no data errors, so if your BIS peaks are below about 80, your disc is quite likely to be readable. Generally, after fresh burns, we demand BIS peaks around 9 maximum, which is very stringent. It didn’t seem repeated treatments provided much benefits – a single round of treatment was sufficient.

In all cases, the heat gun treatment, used judiciously, did not cause any harm and instead improved read error rates. However, I do not take responsibility for anything you do with this information – if you melt your precious disc, or set your house on fire, too bad!

Conclusion

Whatever you do, do not store any type of Blu-ray disc in any form of plastic sleeve – be it written, unwritten, pressed, rewritable. It seems that the sleeves will cause damage to the thinner and more fragile surface of the disc which will cause potentially irreversible data loss. If it’s too late, a heat gun treatment seems to allow for recovery of the data, but does not restore the disc to perfection. Consider yourselves warned.

As a result, I have officially abandoned all use of Blu-ray media for archival purposes. It is not stable enough, or reliable enough depending on the storage method. It’s also not fast enough, and too expensive compared to the cost of hard drive archival. It seems the heyday of optical media is well behind us.

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9 Responses to Warning: Don’t store Blu-ray discs in Sleeves & Heat Gun Revival Technique

  1. Tony says:

    I don’t think Facebook would agree with you about optical media

    http://datacenterfrontier.com/inside-facebooks-blu-ray-cold-storage-data-center/

    • lui_gough says:

      That’s not unusual – commercial users sometimes get certain benefits from different media choices and incentives by partnership to trial such different technologies. Blu-ray has improved since I had first bought into it, and the quality of branded discs are probably sufficient for their needs. The important thing to note is that they are trialing the system at this time, indicating they have little-to-no-hard-data about reliability or whether it achieves the goals they claim it does. From some of the wishy-washy language they use, I’d have to express some doubt – maybe a robotic system loading and unloading 3.5″ archive hard drives might work better for them.

      The reason I say this is because a proper Blu-ray jukebox is not as simple as burning the disc and then storing it, and pulling it out as required. A proper system, for example, will use several elements:
      – A Bluray archival-type drive – e.g. http://blog.cdrom2go.com/2012/01/pioneer-bdr-pr1-archival-blu-ray-drive/ which is more costly, writes slower, and is only really best with archival media.
      – Bluray archival media – e.g. http://www.almedio.co.jp/archive/english/archivedisc/ which are much more expensive per disc.
      – A management system – the system itself incorporates a verification drive and periodic disc testing and data migration when it reaches a certain error threshold. JVC had one made with Pioneer drives but the page has since been taken down, but archived here: http://web.archive.org/web/20150814164551/http://jvc-media.com/archive_bd/index.html.
      – A Bluray inspection-drive – as mentioned above, you need a special type of drive which is capable of reporting the error thresholds before they are critically reached and data becomes lost.
      – A carousel or cartridge to store them in – they are not stored in sleeves or anything half-as-crappy.

      Such systems are often used where WORM properties are most important – e.g. medical X-ray DICOM file archival. However, the cost of such libraries are extremely expensive owing to the higher quality components used, and the energy savings are offset by slower access speeds (read/write) as well as load and unload times, plus the need to periodically scrub the discs to ensure they still meet quality requirements.

      From just basic math, even if they used the most dense BDXL Quad-Layer discs which hold 128Gb per disc, in a similar volume to a 2.5″ hard drive, they could get no more than about 5 discs which is 640Gb of storage. A similarly sized 2.5″ hard drive can store 2Tb, so on density, even the densest discs which cost close to AU$50 a piece cannot compete. Archival media is typically no better than Dual-Layer 50Gb, meaning the same computation only provides 250Gb of storage. Many data-centre operators who are renting space (co-locating) don’t have the luxury of rack space, so this is unlikely to be their first choice on density reasons alone. Because Facebook builds its own dedicated facilities (and possibly in faraway locations in ways similar to Google), they have the luxury to try this technology out.

      I suspect they have reduced the cost of their system by designing it themselves with commodity hardware in ways similar to their own (and Google/Backblaze/etc) deployments, and as a result, while commercial Blu-ray libraries have additional quality assurance features, these would need to be developed “in-house” and I expect their reliability will fall short of commercial systems.

      – Gough

  2. Are M disks also vulnerable to this?

    • lui_gough says:

      I believe they would be, as fundamentally, the reason behind this problem rests in the thin 0.1mm overcoat over the data layer, which is very thin. Its accurate thickness is critical to ensuring the laser can focus on the data layer correctly, and having any form of “patterned” surface resting on it will affect the material.

      That being said, I cannot give a conclusive answer as I haven’t tried it – since my discovery that a good batch of my discs needed the heat-gun treatment, I’ve stored the remainder in other non-contact means.

      – Gough

  3. Jeefa says:

    Why not store the burned discs back to their original (or other) spindle? The discs do not touch each other except at the centre, so there is no pressure exerted on the data layer. The volumetric storage density would be even better than storing them in sleeves. You will have to number the discs and store them in numeric order to ease their retrieval.

  4. Divine says:

    Why not just store them in CD cases or leave them in the original spindle they come in? O_o That’s what I do, so far so good after 4 years of blu ray storage.

    • lui_gough says:

      While I could have, for my use of Blu-Ray discs, it didn’t make sense to do so. With over 500 discs, storing them in CD cases would have bulked up the collection way too much – space is at a premium. As for spindle-storage, not all of my discs came in spindle form. Some came in sleeves – rebagged by Japanese sellers as “sample” sets of media. Regardless, I learnt quickly from my DVD/CD days that spindle storage is not a good idea for where random access to discs is frequently necessary. In the first few years of use, a random disc would need to be accessed once every three days or so which would lead rapidly to fingerprints and scratches especially when in a rush. As a result, I decided to store them in sleeves, as a throwback to the CD days when “as long as they’re not PVC”, they wouldn’t do any damage, while making the whole collection smaller and faster to access.

      I do have some BDs stored in spindles, however, even then all is not that swell. Because the BD discs do not have a hub stacking ring, and the printable coating itself isn’t perfectly smooth or rigid, it seems that my spindle-stored discs have started to get a speckled-bottom appearance which appears to be possible transfer/flaking/outgassing from the printable coating on the disc below transferring to the surface of the disc above. So far, attempts to clean this off have not produced great results – sometimes it causes more smudges to form like an oily fingerprint rubbed across the disc. So far, there haven’t been any total read failures, although it seems that quick testing using LiteOn drives seem to report slightly elevated read error levels. I suspect the nature of spindles (often stored horizontally) means the bottom discs may receive greater pressure and patterning of their overcoats.

      In short, Blu-Ray discs are very much fragile thanks to the 0.1mm overcoat and any storage that results in physical contact to the overcoat is questionable. That being said, data densities with other media are much more enticing, and this is very much for historical reference anywa.

      – Gough

      • Jeefa says:

        “Because the BD discs do not have a hub stacking ring … ”

        You are right, but only when the discs were originally packaged in non-spindle form such as jewel cases. I say this because I have some BD-RE DLs I bought in jewel cases and they appear completely flat. I also recently bought a 50 disc BD-R DL spindle, and while I have not yet opened the spindle I can clearly see some spacing between the discs, even the ones at the very bottom (just like for DVD spindles). It is thus best to buy BDs in spindles and store them back in spindles. If bought in jewel cases then they should be stored back in jewel cases, with a much lower volumetric data density (a third or less). They should not be stored in sleeves as evidenced by your experiences.

        “Blu-Ray discs are very much fragile thanks to the 0.1mm overcoat and any storage that results in physical contact to the overcoat is questionable.”

        True. They are best used for archival cold storage and not for day to day use. For the latter, all their data should also reside in HDDs, which would also serve as secondary backups. Storing them in spindles should not pose a problem as long as they have stacking rings.

        “data densities with other media are much more enticing,”

        Yes. HDDs and SSDs have much higher densities, and as far as I know at this point, HDDs are more reliable for long term storage than SSDs. However, I would only use them as secondary backup and for day to day use. I would not use them as the primary medium for long term archiving, despite their much higher densities. I’ve had some HDDs that have not developed bad sectors after nearly a decade of use, but I’ve also had a couple that did. In fact I have a (FAT32 formatted) 500GB Seagate drive that is less than 2 years old that developed 8 bad sectors smack in the middle of the file allocation table! I was lucky that the other FAT copy was not affected. Anyway, I’m not too keen on placing all my data on at least 2 HDDs (duplicates) and migrating my data every few years to new HDDs. I’d much prefer to store them on 2 duplicate sets of 50GB BDs (or 100GB when prices fall) and store them for much longer. Optical discs are improving their densities. Although not a consumer product, Sony currently produces a 3.3TB Optical Disc Archive cartridge with 11 internal discs (300GB per disc), with plans to increase capacity in future generations.

        • lui_gough says:

          Interesting observations. My early discs were mostly from retail, as at AU$20/disc, it was not fathomable to buy 50 or 100 discs unless you were a commercial facility. In fact, I even had to go to the distributor to direct to get them in sufficient quantities as my local store only stocked around 3-5 on hand. Those were the Riteks which so “famously” failed. I’m not sure but maybe some of my spindled ones do have a ring – but it’s not that noticeable. Unlike the CD-era where it was further out from the centre, it seems it may just be a slightly raised lip in the middle ring. I’m still doubtful it is enough as I find my discs are starting to stick to each other in the spindles, so you get a “peeling” noise as you separate the discs – I think the printable coating may have absorbed atmospheric moisture and swelled slightly. But definitely a better result than sleeves – no failures of spindle-stored discs (yet).

          In fact, initially, they were used to clean-up a hard drive with data that I could have just deleted, but preferred not to do so immediately. As a result, the BD discs became a “last chance” data graveyard which proved more useful over time as some mostly-cold-data began to be stored there (e.g. raw files post-editing that I don’t care about unless a need for a re-edit arises). Even then, I have migrated everything back to idle-hard drives for security owing to the inconsistency in reliability across brands. Right now, I’m finding a number of CMC-made BD-Rs are having oxidation of the reflective layer around the edges, which isn’t encouraging, as I had found TDKs doing the same (but only those bought in retail packs).

          Cartridge based high density storage has been a “talk” for a long time – even a DVD-RAM based one with 10 discs in a cartridge was designed where they eliminated the support-substrate for a glass platter inside the drive and just loaded 0.6mm thick discs. I’m suspecting the same mechanism, extended to BD-XL would produce something like this. Unfortunately, it’s never gained any consumer momentum (most cartridge formats won’t), and the speed/longevity is still an issue – not just longevity of the disc but the mechanism and format itself. I have no doubt that as the optical market continues to wane, exotic drives may become extremely expensive to purchase in replacement, so investment in such a system might cost you more to “clean up the mess”.

          I think the answer, as always, more copies and a periodic “scrub” (verify integrity) and transfer. Whoever said digital data is “easy” to archive definitely hasn’t considered the intricacies of bit-rot, chemical breakdown, magnetic field loss, silent data corruption, file format changes, interface changes and format obsolescence. The only way to guard against it is to be “active” with using and maintaining the data, otherwise, once it’s forgotten, it will be like the Syquest cartridges with Director 3/4 files that came in for recovery – a difficult mess!

          – Gough

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